I'm talking gasoline again today, because, hey, that's what's on a lot of minds at the moment. Here is another simple tip for saving money at the pump:
What little gas you manage to actually get away with isn't going to do you much good, either.
That extra space in your tank is too allow for room for the vapor to expand. If it doesn't have that room , it has to expand somewhere, and in modern cars that is into the vapor collection system. This sounds like it's right where it's supposed to go, but too much all at once can cause the system to become fouled. This can cause expensive repair problems, and, again, a lot of that gas vapor is just going to go right into the air. None of it is actually being used to make your car move, but you paid for all of it and then some.
Topping off the tank is bad for your car, bad for the station pump, bad for the environment, and bad for your wallet. When the pump clicks off, it's telling you that you've got as much as your car can use.
Bonus tip: There's always going to be some evaporation during fill-up, but you can minimize the amount of gas that you pay for that doesn't actually go into your car by filling up before the sun is at its hottest. Plan your trips to the pump in the early morning or after dusk.